Why T-Mobile May Add UMA Calling to Android After All

T-Mobile will reportedly offer calls over Wi-Fi on upcoming Android handsets according to leaked training and screen shots of a Wi-Fi Calling application. The images surfaced on TMoNews, and if accurate, indicate that unlike similar voice over Wi-Fi services that T-Mobile has offered in the past, the Wi-Fi Calling software will not seamlessly transfer calls from Wi-Fi to cellular networks like traditional UMA, Unlicensed Mobile Access, services. Instead, calls on Wi-Fi would be dropped once the handset moves beyond the range of a wireless network.

Earlier this month, Om asked T-Mobile about its UMA offerings because it’s one of the main reasons he uses a BlackBerry device on the T-Mobile network: when in areas of limited cellular coverage, voice calls can be freely handled on Wi-Fi hotspots. A T-Mobile representative mentioned which devices would have UMA support going forward, but didn’t mention Android at the time:

The U.S. arm of the German phone giant is a big supporter of Google’s Android OS, and last week, when I asked a T-Mobile USA representative if there were plans to add UMA to Android phones, he said T-Mobile will continue to support UMA on the current and forthcoming BlackBerry devices and Nokia E73. That’s four models in total. In other words, T-Mobile has no plans on adding UMA to Android phones.

I suspect that T-Mobile didn’t want to tip their UMA hand at that time as the company was prepping a big product launch with the G2: the successor to the original G1. Indeed, the Wi-Fi calling icon found in the leaked screen shots matches up with an icon that allegedly appears on upcoming Android phones for T-Mobile, lending a little more credence to the Wi-Fi calling support. But why would a voice over Wi-Fi app not hand off calls to cellular networks? One of my industry sources shed light on that topic.

Here in the U.S., T-Mobile was the first to offer UMA calling on handsets, giving the fourth largest carrier a way to differentiate against its three bigger competitors. This original UMA solution required specific baseband, or radio chips, indicating a hardware solution limited to the few phones that offered Wi-Fi support. But now that Wi-Fi has proliferated through the smartphone market and operating systems have quickly matured, UMA-like service can be handled through software. Not only is this a cheaper solution for carriers and handset makers, it can be implemented faster as well. Instead of months of hardware design and testing, a software approach can be created, integrated and tested within weeks.

But a software UMA solution is hampered by the lack of service hand-offs to the cellular network. While that sounds like an glaring issue, it may be an overrated one. Industry research on the user behavior of UMA customers indicates that only one percent of UMA calls actually required this handover. Even better: without any chance of such a handoff between Wi-Fi and cellular networks, the UMA service doesn’t have to decide which signal is stronger, and that results in better battery life.

Verizon, Sprint and AT&T have attempted to boost in-home signals with femtocells, or miniature cellular base stations that use Wi-Fi and a customer’s home broadband connection to provide better coverage at home. But T-Mobile hasn’t offered a femtocell. Instead of creating and selling such a device, its more likely that the carrier is building voice over Wi-Fi capability right into the handset through software. Even if these calls are limited to the local home network, Wi-Fi Calling gives T-Mobile a chance to fight for customers who want one phone for both in and out of the home.